This invention relates to interconnecting edge-connected circuit modules to a motherboard.
Computer systems often use a combination of circuit modules that are interconnected to a computer motherboard. In order to reduce the size of the computer system and increase the number of circuit modules that may be interconnected to the motherboard, electrical edge connectors are used to connect edges of the circuit modules to a surface of the motherboard. The electrical edge connector is fastened to the motherboard and retains the circuit module in a position that is substantially perpendicular to the motherboard, so a plurality of circuit modules extending in a direction perpendicular to the surface of the motherboard may electrically communicate with the motherboard.
Conventionally, the electrical edge connector includes a set of electrically conductive pins that are connected to the motherboard through plated holes. In addition, other types of fasteners, such as screws or rivets, are also used to attach the connector to the motherboard. A circuit module for edge connecting to the motherboard includes a circuit board, a set of electrically conductive terminals along an edge of the circuit board, and integrated circuits mounted to the circuit board. The edge of the circuit module with the electrical terminals is inserted into a female socket of the connector, and a latch coupled to the connector secures the circuit module in the socket. The connector has a set of electrically conductive contacts in the female socket that corresponds to the set of electrical terminals on the edge of the circuit module. When the circuit module is inserted into the female socket of the connector, and the latch secures the circuit module in place, each of the edge terminals of the circuit module touches a corresponding electrical contact in the connector. Each electrical contact in the female socket of the connector follows a conductive path to a corresponding pin of the connector, which is electrically connected to the plated holes of the motherboard.
An example of a circuit module that is edge-connected to a motherboard is a computer memory module. Random Access Memory (RAM) may be added to computer systems using memory modules and memory module socket connectors. Typical forms of a memory module are Single Inline Memory Module (SIMM), Dual Inline Memory Module (DIMM), and Direct Rambus(copyright) Memory Module (RIMM(trademark) module).
The assembly process of mounting the memory module socket connectors to the motherboard generally requires a hand-assembly step. Edge connectors of a long length and many pins, such as the 5.5 inch long RIMM(trademark) module socket connector with 184 pins, that need to be inserted into the motherboard are typically placed by hand into the correct location during to the assembly. Afterwards, a wave solder process may be used to secure the pins into the plated holes of the motherboard.
Many components assembled to motherboards in the printed circuit board industry use surface mount pads instead of pins, so the assembly process may be automated. Also, surface mounting the components to the motherboard eliminates the need for soldering the individual pins to the plated holes. Attempts have been made to replace the pins of the RIMM(trademark) connector with surface mount pads and to assemble the connector to surface mount pads on the motherboard. A surface mountable memory module connector could offer advantages including simplified assembly to the motherboard and a reduction in electrical parasitics, such as inductance and resistance. However, the long length of the RIMM(trademark) connector has prevented surface mounting the connector to the motherboard with a high level of reliability. The lack of coplanarity along the entire length of the connector and the motherboard inhibits the reliable surface mounting of the connector to the motherboard.